The present invention relates to a driving circuit of a display, and more particularly to a driving circuit of a flat panel display and a driving method thereof.
In a recent information-oriented society, the importance of display devices used as visual information conveying media has been emphasized. However, cathode ray tubes (CRTs) that have been widely used have major disadvantages in regard to their large size and weight. A variety of flat panel panel displays, which can overcome the limitations of the CRTS, such as a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), and an electroluminescence (EL), have been developed and put to practical use.
The LCD displays an image by controlling an electric field applied to a liquid crystal layer in response to video signals. As the LCDs are thin and flat panel display devices having low power consumption, the LCDs are used as displays for portable computers such as laptop computers, office automation devices, audio/video devices, indoor/outdoor advertising display devices, and the like. As the LCDs have a slim characteristic and a lower power consumption characteristic, the CRTs have been quickly replaced with the LCDs. Particularly, LCD panels that drive liquid crystal cells using thin film transistors provide clear image quality and have low power consumption. Recently, development of production technology and achievement of research make it possible to provide large-sized, high resolution LCD panels.
FIG. 1 is a circuit diagram of a typical driving circuit of a flat panel display.
Referring to FIG. 1, the typical driving circuit includes data processing units 11, 12, 13, and 14 for converting and decoding data signals, amplification driver units 21, 22, 23, and 24, a switch unit 30, and a charge sharing unit 40. Here, the converting is performed to convert a digital signal into an analog signal. The data processing units 11, 12, 13, and 14 are classified into data processing units PDAC for processing positive gamma values and data processing units NDAC for processing negative gamma values. The amplification driver units 21, 22, 23, and 24 amplify signals output from respective corresponding data processing units, improve driving capability of the signals, and transfer the signals to the switch unit 30. The switch unit 30 is provided to transfer the signals output from the amplification driver units 21, 22, 23, and 24 to nodes A or nodes B. The signal passing through the switch unit drives unit elements of the flat panel display that are assigned to a corresponding channel via one of nodes A and B from said pair of nodes.
When the signals passing through the switch unit are transferred to the channels via the nodes A, the flat panel display is driven in the form of PNPNPN. When the signals passing through the switch unit are transferred to the channels via the nodes B, the flat panel display is driven in the form of NPNPNP.
The charge sharing unit 40 is provided for sharing electric charges of all the nodes A or all the nodes B after the signals passing through the switch drive the unit elements of the flat panel display.
A display using liquid crystal is driven with positive and negative values alternately to increase the service life of the liquid crystal. When each of the channels has both of a circuit driven with the positive value and a circuit driven with the negative value, a circuit area of the driving circuit and a power consumption increase. Accordingly, as shown in FIG. 1, the circuits driven with the positive value and the circuits driven with the negative value are alternately arranged and driven for the respective channels through a switch unit 30.
Meanwhile, a user recognizes an image nonlinearly rather than linearly. Therefore, there is a need for the conversion of linear display information into nonlinear display information. A gamma correction method has been widely used for the conversion. The data processing units PDAC and NDAC of FIG. 1 output gamma values that are obtained by gamma-correcting input data of display information. At this point, the data processing units PDAC outputs positive gamma values and the data processing units NDAC outputs negative gamma values.
The above-described driving circuit of the flat panel display is designed to amplify the signals that are decoded in the data processing units, improve the driving capability of the signals, and transfer the signals to the corresponding channels via the switch unit. The channel is one column of the flat panel display. The switch unit is generally formed of a metal oxide semiconductor (MOS) transistor. In this case, the signal is attenuated due to a turn-on resistance of the MOS transistor in the course of passing through the switch unit. In order to solve this problem, the driving capability of the signals output from the amplification driver units must be sufficiently improved or the turn-on resistance must be reduced. To realize this, a size of the MOS transistor for the amplification driver unit or the switch unit must be increased. This causes increase of the circuit area of the flat panel display.